i have a question about training the body to use more fat as fuel in endurance efforts.
my experience and research tells me that this adaptation is very usefull for ultra distance athletes, but i have always used LOTS of LSD training to achieve it in the past. as i have switched to a more CF approach to training i am wondering what i can do to maximise my gains in this area, without doing TOO much LSD (i actually enjoy some).

my thoughts so far:

a. low carb diet with LOTS of fat.

b. doing 60-90 minute moderately paced efforts in a fasted state.

c. pre-exhausting the glycogen in the specific muscle groups beforehand. (say squats before a bike ride or jump rope before a run.)

if it matters my diet now is about 50% fat 25/25 protien and carbs with a 3rd of those carbs coming post workout as per some of Robb Wolfs recommendations. i commute on my bike and am doing a strength biased version of CF at the moment.

im getting set to do a marathon, a 50 miler, and a 12 hour MTB race in the next 6 months its gonna be AWESOME!!

any feedback recommendations?

Hi Dylan

I don't think the science is conclusive in this area yet. Any type of aerobic training will train fat metabolism. Trained muscles are better at burning fat and tend to store more intramuscular fat. This happens no matter what you eat. It is unclear whether training in a fasted state or after consuming fat will enhance this adaptation further. It is known that exercising after a fat meal will lead to an increased reliance on fat rather than carbohydrates.

A few suggestions....If you are on a low carb diet, you can take advantage of whatever adaptations you have and still maximize gyycogen storage, just in case. Continue to eat low carb but 3 days before your race, consume plenty of carbohydrates to maximize muscle glycogen stores for 2 days while you are tapering. Then on race day, consume your traditional high protein, high fat meal prior to the race to stimulate fat oxidation during the run (you burn what you eat immediately prior to the race). The glycogen that you stored in your muscles 2 days prior will still be there but your body will want to burn fat first, since that was what you ate pre race.

Once carbs are moved into the muscles, they are effectively trapped inside of the muscles and cannot be used to increase blood sugar (unlike liver glycogen). They must be burned by the muscles to fuel activity. This is good because it will be available for you during your run. You get the best of both worlds, muscles full of glycogen with the fat oxidation adaptations from a low carb diet and low carb/high fat meal immediately before competition. You might need that stored glycogen in the final few miles.

This has been shown to be effective in rats but I am not sure that there are enough human studies to say for sure that it is optimal. However, it is a low risk approach for somebody already on a low carb diet.